Controlling wheel hop in a vehicle driveline

1. A method for controlling wheel-hop in a vehicle driveline, comprising:

detecting that a wheel-hop condition is occurring upon determining an amplitude and frequency of speed oscillations of a one-way clutch that transmits power to wheels of the driveline; and

engaging transmission friction clutch that is hydraulically actuated, arranged in parallel with the one-way clutch, and transmits torque in the driveline between an engine and the wheels.

2. The method of claim 1 , further comprising reducing engine output torque transmitted to the wheels if the speed amplitude is greater than a reference speed amplitude.

3. The method of claim 2 , wherein the reducing step comprises adjusting at least one engine parameter including engine airflow, engine throttle position, engine ignition timing and engine air-fuel ratio, or any combination of these parameters.

4. The method of claim 1 , wherein the driven wheels are driveably connected to a transmission output shaft and the determined amplitude and frequency are the amplitude and frequency of the output shaft speed.

5. The method of claim 1 , further comprising:

if said amplitude and frequency are in a range indicating that a wheel hop event is occurring, incrementing a counter containing a running total of wheel hop oscillations the driveline has experienced; and

if said amplitude and frequency are in a range indicating that a wheel hop event is not occurring, decrementing the counter.

6. The method of claim 1 , further comprising determining and recording a number of wheel-hop speed oscillations that occur during each wheel-hop event and the amplitude of each corresponding wheel-hop speed oscillation.

7. The method of claim 1 wherein the step of determining the amplitude of speed oscillations comprises:

establishing a reference decrease in amplitude that must occur following each peak amplitude that occurs during an oscillation;

when the reference decrease in amplitude occurs, determining that the amplitude of the oscillation peak that immediately precedes the reference decrease is the amplitude of the oscillation.

8. The method of claim 1 wherein the step of determining the frequency of speed oscillations comprises:

determining at a constant speed amplitude a period length between falling edges of consecutive speed oscillations; and

setting the frequency equal to an inverse of said period length.

9. The method of claim 1 wherein the step of determining the frequency of speed oscillations comprises:

determining at a constant speed amplitude a period length between rising edges of consecutive speed oscillations; and

setting the frequency equal to an inverse of said period length.

10. A method for controlling wheel-hop in a vehicle driveline, comprising:

detecting that a wheel-hop condition is occurring upon determining an amplitude and frequency of speed oscillations of a one-way clutch that transmits power to wheels of the driveline;

engaging a hydraulically actuated transmission friction clutch arranged in parallel with the one-way clutch and that transmits torque in the driveline between an engine and the wheels; and

reducing engine output torque transmitted to the wheels if the speed amplitude is greater than a reference speed amplitude.

11. The method of claim 10 , wherein the reducing step comprises adjusting at least one engine parameter including engine airflow, engine throttle position, engine ignition timing and engine air-fuel ratio, or any combination of these parameters.

12. The method of claim 10 , wherein the driven wheels are driveably connected to a transmission output shaft and the determined amplitude and frequency are the amplitude and frequency of the output shaft speed.

13. The method of claim 10 , further comprising:

if said amplitude and frequency are in a range indicating that a wheel hop event is occurring, incrementing a counter containing a running total of wheel hop oscillations the driveline has experienced; and

if said amplitude and frequency are in a range indicating that a wheel hop event is not occurring, decrementing the counter.

14. The method of claim 10 , further comprising determining and recording a number of wheel-hop speed oscillations that occur during each wheel-hop cycle and the amplitude of each corresponding wheel-hop speed oscillation.

15. The method of claim 10 wherein the step of determining the amplitude of speed oscillations comprises:

establishing a reference decrease in amplitude that must occur following each peak amplitude that occurs during an oscillation;

when the reference decrease in amplitude occurs, determining that the amplitude of the oscillation peak that immediately precedes the reference decrease is the amplitude of the oscillation.

16. The method of claim 10 wherein the step of determining the frequency of speed oscillations comprises:

determining at a constant speed amplitude a period length between falling edges of consecutive speed oscillations; and

setting the frequency equal to an inverse of said period length.

17. The method of claim 10 wherein the step of determining the frequency of speed oscillations comprises:

determining at a constant speed amplitude a period length between rising edges of consecutive speed oscillations; and

setting the frequency equal to an inverse of said period length.

18. A method for controlling wheel-hop in a vehicle driveline, comprising:

transmitting power from an engine through a one-way clutch arranged in parallel with a disengaged friction clutch to the wheels of the driveline;

detecting that a wheel-hop condition is occurring upon determining an amplitude and frequency of speed oscillations of a transmission output that transmits power to wheels; and

engaging the transmission friction clutch.

19. The method of claim 18 , further comprising reducing engine output torque transmitted to the wheels if the speed amplitude is greater than a reference speed amplitude.